Sandblast stencil



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N0 5 1946.- A. J. wARTHA sANDBLAsT sTENcn.

. Filed Jan. 11. 1940 Patented Nov. f5, 1946l 2,410,472 v Y sANDBLAs'rsTENcIL Alfred J. Wartlua St. Paul, Minn., assigner to v MinnesotaMining & Manufacturing Company, St. Paul, Minn., a corporation ofDelaware Application January 11, 1940, senat No. 313,370

(el. iig-3c) 23 Claims.

This invention relates in general to sheet materials and moreparticularly to improvements in such sheeted materials as described inmy applications Serial No. 358,443, iiled September 26,

1940, ,and issued to Patent No. 2,251,647 on August 5, 1941, Serial No.275,595, filed May 25, 1939, and

I Serial No. 275,596, led May 25, 1939, issued to Patent No. 2,251,646on Augustl 5, 1941, wherein the sheeting is of a nature to be inherentlyresistant to abrasion, such as it would be subjected to when used as astencilfor Sandblasting operations, and especially to such materialsprovided with an adhesive coating which is also characterized byresistance to abrasion and is desirably of a pressure-sensitive nature.-Furthermoreythe adhesive is preferably water-insoluble and normallynon-drying. -While the invention is de- 'scribed and claimed withrespect to'a sheet material particularly adapted for use in makingstencils, it will be understood that the sheeting may be employed forother purposes, andthe invention therefore nds a wide field of utility.

The invention has special utility as stencil material for .limiting theapplication of fluid in the form of spray or otherwise, and also forlimiting the area of a given lsurface exposed to the action of sandparticles in a sandblasting operation, it being understood, however,that such limited elds of specific use are cited merely for pur'-` posesof illustration as examples of the utility of the invention in itsseveral phases. A prime requisite of stencil material to be used ininscribing stones, such as granite or marble, Iby Sandblasting. is thatit must be sufficiently strong and resilient to resist abrasion by astream under an air pressure of 100 pounds.` It must be flexible toconform to extremely unevensurfaces on which it may be applied. It mustbe tough enough to withstand abrasion and yet it must be capable ofbeing readily and accurately cut to form a stencil aperture of anintricate design. It must adhere to the surface to be inscribedflrmlyenough to prevent its displacement during the Sandblastingoperation and yet not so strongly as to injure the surface or causeadhesion thereto of particles of the stone surface upon its removal. Theprin,-

- cipal object of the invention is to provide a sheet blasting-resistantliner adapted to take pencil and and characterized by a resistantbacking coated on one surface with a carbon impressions and .bepermanently retained thereon and on its opposite side with an adhesivehaving blast-resistant properties and which is of -a pressure-sensitivenature adapted to retain the facing the stone surface in compositionhaving the foregoing highly desirable qualities. A further importantobject' of the invention is the provision of sheet material of thecharacter described which can be produced relatively easily andinexpensively.

One of the principal objects of the present invention is to providesheet material adapted for making stencils for use in the stoneengraving industry Where Sandblasting operations are used,

backing material on the'surface of the stone to vwhich it is applied toa degree suiiicient to resist any action of the sandblast to remove thesame, but at the same time permitting the stencil sheet to be readilyremoved when desired without deany way.

Other objects and advantages of the present invention reside in theprovision of a stenciling sheet which possesses .unusual durabilityunder the high pressures employed in pressure blasting; the provision ofan improved adhesively coated stencilable sheet in which quickapplication of the same to a desired surface, including a cold surface,may be made in any-kind of weather; the provision of a stencilable sheetand adhesive therefor in which the adhesive and the sheet arenon-hardening and in which the adhesive is pressure-sensitive; theprovision of an improved form of stencil sheet which permits, in high-Vpressure sandblasting methods, of highly accurate work by the operatorand to permit the operator to do what is known as ne edge or shapecarving; the provision of an improved form of stencil sheet in which theadhesive employed possesses a high degree of tenacity for the surface towhich it is applied, thus preventing the stencil from leaving the stonewhile blasting and, at

the same time, in which the adhesive will not` oiset onto the softerstones or pull away particles of the stone when itis removed therefrom.

The invention is disclosed in two principal em-` bodiments, each ofwhich is characterized by the provision of several laminations having avbacking capable of readily yreceiving and retaining marking, such as areused as transfers in the monument trade or a design drawn with anordinary lead pencil;. and in'which such a stencil sheet -may beemployed as a. substitute for sci-called oil?- set blanksemployed bylithographers. In one embodiment, the layer of highly blast-resistantmaterial is coated on one side with an adhesive adapted to be attachedto the stone or other article to be inscribed, and on the other surfacean adhesive to which is secured a layerv of treated paper' or clothwhich has a back sizing capable of readily receiving and retainingmarking. The

' other embodiment is somewhat similar, and one surface of the-highlyblast-resistant layer is provided with the back sizing vcapable ofreceiving tough, exible, blasting and retaining marking and the othersurface with an adhesive to which is secured a layer comprising Troyatissue or a thin cellulosiolayer having similar properties coated withan adhesive adapted 4to secure the composite to a stone or other surfaceto be inscribed. Removable liners of parchmentized paper and starchedHolland cloth to protect the adhesive .coating while the sheet is inroll form are disclosed in my cepending applications previously referredto. The presentA invention represents an improvement over theseVconstructions in that the diiilculty of removing parchmentized paperliners and Holland cloth liners from the adhesive .is eliminated. Theprovision of a permanently secured liner permits the usage of a thinnerstencilsheet backing than in previous sandblest stencilk sheets known tothe art without loss of blast-resistant properties.

The invention wil be readily understood from the following descriptionin conjunction with the accompanying drawing wherein certain preferredembodiments are shown, in` which:

Fig. 1 is a plan view of the stencil sheet material with apertures cuttherein to provide a design: Y

Fig. 2, an enlarged sectional view taken along the lines 2-2 of Fig. 1and showing the improved stencil sheet material provided with aperturessecured to a slab; A

Fig`r3, an enlarged sectional view of a modied forni of the stencilsheet secured to a slab;

Fig. 4, an enlarged sectional view of a further modified 'form of thestencil sheetsecured to a slab.

vcompatible with the backing so as to have greatery A satisfactoryconstruction, shown in Figs. 1-3, embodying the foregoing highlydesirable results 4 naphthol maybe omitted if desired. but the mostsatisfactory results have been obtained in following the formula asherein set forth.

Factice is a vulcanized or blown oil which mixes evenly with the rubberto increase the homogeneity ofthe mass and also serves to reduce thenerve of the rubber. 'Ihis latter function is important in that theordinary characteristics of rubber as to toughness and elasticity arenot desirable in this composite sheet as they would cause the sheet tobe difficult to cut accurately to the desired design. Vulcanizedvegetable oils (factice) have been found to be particularly suitable forthis purpose. For example, such vegetable oils as vulcanized linseedoil, tung oil, cottonseed oil, corn oil, and sunflower seed oil havebeen found to be satisfactory. The reduction of the nerve of the rubberis further accomplished by the intensive milling in the preparation ofthe composite material as hereafter disclosed. Solros is a heat-treatedwood rosin used in this composition as a tempering agent particularlyduring the milling process.' Other rosins may be employed and mineraloils may be employed, in whole or in part, to replace the vulcanizedvegetable oils. Beta naphthol is an antioxidant used to prolong the lifeof both the rubber and the glue of this composition.. f

The fibrous fillenwhen used, is preferably of a nature which permits offree cutting of the material, as cotton linters, paper fibre, wood nbre,

' grass fibre, or mixtures thereof, and the like.

' thiuramtetrasuliide, selenium, m-dinitrobenzene,

For vulcanizing the compounded sheeting, if desired, such agents ascommonly used for that lpurpose may be utilized, viz., for example,sulphur or sulphur-bearing agents as dipentamethyleneand the like, withor without the inclusion of an accelerator, as, for example, diandtrlphenyl- 40 guanidine, tetramethylthiuram and piperidine adhesion forthe backing than for a surface to which the stencil may be applied. Tothe oppositesurface of therubber sheet in this embodiment is applied atreated sheeting preferably of cellulosic material having a coatingcapable of taking pencil and ink impressions by transfer and noliadapted to offset adhesive'thereon when ro ed.

In the other embodiment shown in Fig. 4, likewise of a laminatedconstruction, the coating adapted to receive impressions is applied as abacksizing to the rubber composition sheet.

In all of the embodiments, the rubber com.- pounded-backing sheetisconvenientlymade up from a rubber compound including rubber such aslatex crepe, which may be vulcanized, Whiting, bone glue' siftings,Solros, factice and beta lnapl'ithol with or without fibrous material.In

this composition the writing provides a finely divided base materialwhich is bonded together to form a coherent mass by the rubber. v'Othercomminuted base materials, such asDixie clay,

. soapstone and the like', may be employed instead of writing, in wholeor in part. The bone glue siitings are a convenient form of finelydivided glue which serves as a bodying ingredient in addition to theWhiting, 'and also gives firmness togthe 'composite sheet which enhancesthe ease and accuracy of cutting apertures yin the sheet to form thestencil., TheA ,glue Solrosv and beta derivatives.

While the proportions of these ingredients may be varied withinreasonable limits, I have found proportions by weight Iaccording to thefollowing formula to give a desirable Acomposite sheet material:

FORMULA A For my purposes it' is preferred to place the rubber in a milland then mill it until the massv follows the mill roll and gives theappearance of a smooth film covering the roll This takes approximatelyten minutes of milling time.

The bone glue siftings are then added andthe rubber and glue, insubstantially equal amounts, milledfor approximately-thirty minutes.From time to time the mass may be treated with steam applied directlythereto, thus moistening the glue content andcausing the same to morerapidly melt into and mixwith the rubber.

, I then mix thoroughly together the factice,

Whiting, lSolros and beta naphthol and when well mixed they are added tothe rubber-glue mass.

4.This mass -is then milled under steam application untiltheentire'batch is thoroughly homogenized.

When the composite mass made 'according to the above formula has beenthoroughly mixed, it

andere 5, is then sheeted or calendered 'the desired thickness. which,for example, me?

be approximately .035 inch. This sheet isthen tent and obtain a workablesheeting;

with no van'ation in the aging inhibitor. when desired, there may beadded ibrous material in.

proportions varying from .5 to 80 parts and/or in either case thecompounded material may be vulcanized in a manner well known in the art.

To make a fibrous type sheeting or compounded material of the nature asherein described,

after obtaining a homogenized mass by compounding the material ofFormula A, fibrous material in the form of cotton linters; either dry ormoistened, for example, is slowly added to the mass, preferably in theproportion of- 1 part iibre to 2 parts compounded mass and milled ormixed until thoroughly incorporated therein, as fully de scribed in mycopending application Ser. No. 275,595, led May 25, 1939. Thisproportion of libre preferably is the maximum desired, and I have foundthat for some purposes as in blasting glass, where sheetings of .011inch in thickness may be used, the libre content may be reduced totoform-ash/etof Parts Bone glue siftings 10 to 25 Rubber content 10 to40Whiting 30 to 'l5 Rosin .45to 1 Factice 2.50 to rubber as contained inthe aforementioned formula:

Parts Zinc oxide 5 Stearic acid 3 Sulfur 3 Accelerator "D, P. G.(diphenylguanidine) l mixed by milling with the compound of Formula Aforapproximately minutes and sheeted and Vvulcanized at 250 F. for twohours. In addition.

the vulcanized sheet material may be a composition mixed in thefollowing proportionate parts:

Parts Formula A 530 Zinc oxide 25 "D. P. G. accelerator 1 Sulphur 4which may be mixed by milling for approximately -30 minutes, thensheeting it and vulcanizing it at 250"A F. for approximately six hours.or for longer periods of time at lower temperatures.

As a substitute for the vulcanizing agents expressed above, I may use asulfur bearing compound, such as Tetrone A(dipentamethylenethiuramtetrasulde), or the like, milled directly intothe compounded plastic stock with subsequent sheeting and vulcanizlng ata temperature.

of approximately 250 F. for a period of two fractional parts andsatisfactory results obtained.

for approximately 24 hours to impart irmness thereto.

In order to obtain a vulcanized rubber sheetin the compounded materialmay have vulcanizing agents and accelerators included by mixing theminto the mass during its compounding, or the hours.

The antioxidant, vvulcanizing agents and their accelerators as expressedare illustrative examsheeted to .022 inch thickness, more orless, as

desired.

After a backing of the above composition has been formed with or withoutvulcanization and ythe inclusion of fibrous material, the resultant Ysheet, of the-embodiments of Figs.2 and 3, is

provided on one side with a liner adapted to be permanently retainedthereon and on the opposheeting may be treated with vulcanizing agents,

as described in my copending application, Ser. No. 275,596, filed May25, 1939, issued to Patent No. 2,251,646 on August 5, 1941. For example.after cooling, the sheeted material may be treated with site side withan adhesive preferably of a pres-Y sure-sensitive character whichrequires no actipressions, can be cut readily with a knife'and willprevent oisetting of the tacky adhesive coating on the opposite side ofthe sheeting'when in contact therewith, when the sheet material is laidout and a coating of sulfur chloride is' brushed or sprayed onto itsexposed surface and allowed to stand until vulcanized However, I mayimmerse or subject both surfaces to the solution to obtain a faster andmore thorough vulcanization upon evaporation of the solvent and reactionof the sulfur chloride, with a vulcanizable material contained in thecomposite sheeting.

Alternatively, when a compoimded backing completely vulcanized ispreferred, I incorporate, for example, with the Formula A, following itscompounding, stock curing or vulcanizing materials ofthe followingcharacter d in proportionate parts by weight based on parts l Oleumspiri is rolled or` stacked.

The liner of the embodiments of Figs. 2 and 3' is a treated cellulosicmaterial which is preferably a porous paper or cloth, as for example, a

long bre rope paper, such as Manning rope stock paper or the like,unified by treatment with a saturating solutionvof the followingcharacter expressed in approximately proportionate parts by weight as:

Y 7 A prepared by mixing and churning until the viscosity isapproximately between 15-18 secs. at 100 F. The paper or cloth issaturated with this composition in the usual manner of impregnation and,when properly dried, is backsized with a material which takes pencil orink transfer impressions and is preferably made up as a solution of glueor a cellulose derivative such as ethyl cellulose, cellulose acetate,cellulose xanthate or cellulose nitrate, with or without a suitableplasticizer such as dibutyl phthalate. A suitable formula inproportionateparts byweight is as follows:

. FORMULA C Parts Ethyl cellu1ose .6 Ethyl alcohol 2. Acetone .6

prepared by cold mixing and coated to the treated paper backing bywell-known coating methods. To this composition, during mixing, may beaddedsweflling agents, as zein or the like, placed in solution wit-hwater and ethyl alcohol, to aid in transferring prints. Other backsizecoatings adapted to receive transfer impressions of the designs to beblasted are sheliac, casein, vinyl resins, and zein a corn productdissolved in alcohol and water; these coatings are not as desirable asthose first mentioned.

After proper drying by evaporation of the solvents, a pressure-sensitiveadhesive, as for example of the rubber-resin type of character, asherein described in Formulas D, E, F, with or without Whiting, iscoatedonto the face side of the pre-treated paper and set-up by theusual methods known to the practice, whereupon the prepared sheeting isapplied by conventional .means to the compounded backing for pennanentthe side opposite the liner with a pressure-sen-V sitive adhesivecontaining ingredients which are similar to those used in the backing.Due in part to this similarity an'd in part to the nature yof theadhesive compound, the bond which results when the adhesive is appliedto the backing is of such strength that it is practically impossible tocause subsequent separation by mechanical means. This condition preventslamination or'separation even under the most adverse treatment. y

An illustrative formula for an adhesive by weight may be:

FORMULA D Pounds Latex crepe rubber 40 Zinc oxide 20 Whiting 20 Solrosrosin 26.7 Beta naphthol .4

The process of making the adhesive which I prefer to employ for thepurpose of this invention preferably is carried out by running thethroughout the latex crepe. I then add the Solros rosin and subject thewhole batch to a'thorough mixing. The batch is then removed from themill with a scraper and may be stored in ,trays with a powdered lineruntil ready for application to the sheeted backing by heating andcaiendering.

In this formula the relatively large ratio of pigments, such as zincoxide and Whiting, serve to make the adhesive blasting resistant, andthe resin ,in this case serves as a tack-producing ingredient to givethe adhesive the desired normally tacky character.

A softer pressure-sensitive adhesive, which is applicable to coldsurfaces' as cold stone, and to other surfaces, may be employed and is acomposition of the following character:

Femmina E Part 1 Pounds Smoked sheets 50 Zinc oxide 25 Pine tar 3 ResinV.5 Beta naphthol .5 Peptizing agent 0.15

prepared by milling the smoked sheets on a standard production mill atthe approximate temn perature of F. until smooth and then adding .lyrequires a minimum of 30 minutes.

To the composition of Part 1 is further added a plasticizing agent andadditional tack-producing resins in the following proportionate parts:

Part 2 Pounds Part l-- 4.35 Plasticizer (stearic acid) .50 Rosin (waterwhite) 1.24 Solros rosin .41

compounded by further milling until the product is uniformly plastic andadhesive whereupon it may be calendered to the yprepared backing orstored, as previously indicated, and later warmed for caiendering.

An adhesive of a vulcanized pressure-sensitive type possessing suchcharacteristics as to render the compounded backing particularlysuitable as a pressure-sensitive adhesive sheeting may be, for' example,a composition comprised of the following:

FORMULA F Grams Latex crepe 1000 Zinc oxide 200 Peptizing agent 2Antioxidant 25 Plasticizer 5 Vulcanizing agent .'lf

prepared by milling the crepe and zinc oxide for approximately 4 minutesat 20 lbs. steam pres-V sure, adding the peptizing agent, such as RPA#2, a commercial mercaptan (naphthyl beta mercaptan), "or-otherpeptizing agents. such as tion, and it mately 30 minutes. Thiscompounded crepe composition is thenV removed from the milling 20 hoursat approximately 250 F. tc 260 F.. at which time the vulcanizing agent,preferably a prepared sulfur-bearing compound as Tetrone A"(dipentamethylenethiuramtetrasuliide) mixed with 500 grams of a fillersuch as Dixie clay, is added with continued mixing for an additionalhour or until such time as is necessary to Vulcanize the adhesive. Thisvulcanized material is then removed from the mixer-and calendered in theusual manner of calendering onto the stencil sheet backing. The desired.

The adhesives of the foregoing formulae possess great tenacity, and Ilnd that, for some purposes, I am able to reduce its tenacity and yethave it retain the desired degree of adhesion to a surface to which itis applied by reducing the adhesive character v thereof. This isaccomplished, for example, by increasing the proportion of filler,Whiting or the like.

Referring now more particularly to the draw-l ing, a preferred form ofthe stencil sheet is illustrated in Figures 1 and 2, wherein thereference character d indicates a backing'sheet which may be formed froma composition of Formula A comprising comminuted base material bondedtogether by rubber and a rubber modifying agent, or may comprise thecomposition of Formula A and fibrous material, or a vulcanized rubbercompounded backing sheet, as previously fully described. One surface ofthe backing sheet is provided with an adhesive coating 5 which is of arubber pressure-sensitive nature and may be made lin accordance with theadhesive formulae herein set forth. To the other surface of the backingsheet is secured a treated paper liner 6 adapted to be permanentlyretained thereon during the Sandblasting operation due to the interposedadhesive layer 1. The upper exposed surface of the liner is providedwith a thin coating 8 adapted to receive markings and transfer designsto facilitate cutting the desired stencil openings and may comprise acoating prepared in accordance with Formula C, previously stated, or

prevent offsetting of the pressure-sensitive adhesive 5 when the stencilsheet material is rolled prior to its application to a surface to beblasted and need not be removed when the stencil is to be applied to asurface, such, for example, as the slab of marble 9, shown in Fig. 2.The design forming apertures I 0 and Il may be cut in the compositestencil sheet either before application to the surface of the slab orafter` such applicawill be understood that the design to be cut in thestencil sheet may be applied to the liner coating 8 by pencil, pen,transfer or other instrument prior to or after application of thestencil on the slab.

When the stencil sheet is applied to the surface of a slab 9, theadhesive coating tenaciously adheres to this surface and is adapted toprovide dams I2 along the margins oi' the stencil apertures I0 and l I,so that the sandblast strihng rolls and placed -in an `internal mixer,such as a Baker-Perkins Mogul machine, and mixed for filler" may beomitted if the exposed surface of the slab through these openings willcut recesses corresponding in shape to the openings and will not deflectand cut away under the stencil sheet itself.

Due to the resilient nature of the adhesive 5, the backing sheet t andthe liner 6, the particles of sand striking the exposed surface coating8 of the liner 6, and striking the walls of dams l2, are caused to berepelled or deflected without substantially wearing away this surface.

Referring to the embodiment shown in Fig. 3,

this construction is similar to that of Fig. 2 except that the liner i3is formed of cloth, preferably treated in the manner previouslydescribed, instead of paper. The cloth liner is provided With a thincoating 8 adapted to receive markings and transfer designs, and theliner is secured to the backing sheet 4 by an adhesive layer l. Thebacking sheet i and the adhesive 5 securing the backing to the surfaceof the slab 9 are preferably formed of the compositions previouslydescribed.

By virtue of the permanent liner, I am able to produce a flexible, toughand resilient sandblast stencil sheet that is thinner than those knownto the art, and which, because of these properties, adequately-resistspenetration and wearing away by reason of the h'igh velocity sandparticles used in Sandblasting operations.

Referring to Fig. '4, wherein a sandblast stencil backing sheet havingproperties similar Ato but of a different laminated construction thanthe embodiments of Figs. 2 and 3, is shown adhesively aiiixed'to `thesurface of a. stone 9. Generally this embodiment comprises a laminationof a thin liner of treated paper `it or like material coated on bothsurfaces, having some blast resistant properties but insufficient towithstand alone sandblasts employed in the monumental trade, and a.relatively `thicker layer of a composition I5 more resistant to theaction of a sandblast than the liner It, said layer l5 being provided onits exposed surface with a back size IB. The liner Ml is preferably aTroya tissue .002 inch thick, although it may comprise a thin layer ofDexter tissue or other paper of suitable strength and thinness-oxfCellophane or cellulose acetate. The Troya tissue liner I@ is ment witha saturating solution to prevent splitting of the liner ld when it isunwound from the roll prior to usage; such solutions are preferably of arubber resin base which accordance with the following formula:

FORMULA G Latex crepe rubber pounds 250 Zinc oxide do 250 No. 10 rosindo 400 vlBeta naphthol do 2.5

Solvent-such as oleum spirits or heptane gallons-- v82 The latex crepeand zinc oxide are rst milled to uniformly incorporate the zinc oxide inthe milled rubber, and the krosin and beta naphthol are then added andthe mixture is then completely disolved in the solvent which may beoleum spirits or heptane. The Troya tissue liner is saturated with thiscomposition in the usual manner ofimpregnation.v Other saturatingsolutions may be employed,.for example, solutions employing reclaimedrubber, gum and a filler which may be Whiting in place of zinc oxide.Satisfactory results have also been obtained by 7 employing a saturatingsolution such as Formulav first unified by treatmay be prepared in Theliner I4 is then coated on bothsurfaces Il, I8 with a normally tackyadhesive which may be of the composition set forth in Formulas D,

E or F or may be prepared according to the following formula:

The process of making lthe Aadhesive which I4 prefer to employ for thepurpose of this invention preferably is carried out by running the latexcrepe rubber for six or seven minutes in a mixer. The zinc oxide and 40parts of.. No. 10 rosin, to' gether with the beta naphthol and mixtureA,

12 a corn product dissolved in alcohol andwater; these coatings arelikewise adapted to receive transfer impressions of the designs to beblasted ibut are not as-desirable as those previously mentioned.

From the foregoing it will be understood that the invention may beproduced in several diiferent forms, that is to say, the stencil sheetmay be a straight compounded material or a compounded materialcontaining fibre and either prepared in a vulcanized or unvulcanizedstate, the sheet material having on one side a liner adapted to bepermanently retained thereon.

- As an alternative-formula. for the compounded backing, I have hadsuccess with a composition wherein the quantity of factice or a similarvul- .canized or oxidized vegetable, mineral or animal are then addedand the mixing carried on until the materials are completely dispersedthroughout the latex crepe. a mixture of 3 parts of condensation productof acetone and aniline, such as sold vunder the trade name Flectol H,and 5 parts of latexcrepe, which are thoroughly mixed before being addedto the pigmented rubber-rosin batch.

The mixture A" comprises The material is then dissolved in a suitableamount of heptane and the 2 parts of the solution of wood rosin are thenadded and thoroughly mixed in with the other' ingredients.

After the liner I4 has been coated on both of its surfaces with theforegoing adhesive or any of the other previously mentionedl suitableadhesives, its calipreis approximately .005 inch.

The blast-resistant layer i5`may be prepared in accordance with FormulaA herein, or it may comprise Formula A and the fibrous material as setforth in my copending application Serial No. 275,595, or it may comprisethe vulcanized material as described in my copending application SerialNo. 275,596, filed May 25, 1939, issued to Patent No. 2,251,646 onAugust 5, 1941, as previously set forth This material compounded insheet form, approximately .035 inch thick, is provided on one surfacewith a back sizing coating I6 which may consist of a glue coating,preferably comprised of hide glue in a solution containing 1 part glueto 3 parts of water, or theback sizing may be prepared in accordancewith Formula C herein or it may be formed of a solution of celluloseacetate or cellulose nitrate with or without a suitable plasticizer suchas dibutyl phthalate. y

The layer I5 with the backing sizing I6 is -adhesively combined with thedouble coated liner Il as the liner I4 emerges from the coating machine,the back sizing I6 remaining on the exposed surface, as shown in Fig. 4.As indicated in the drawing the adhesive coating I8 serves to retainthecomposite sheet on the surface to be inscribed without activation of theadhesive. i'

The composite stencil sheet construction shown in Fig. 4 is particularlyadvantageous when the layer I5 comprises the vvulcanized materialpreviously described, inasmuch as the thin liner I4 tends to inhibit theundesirable stretch of the vulcanized material.

The transfer receptive properties of the back sizing I6, when itcomprises a, glue coating, may -be enhanced by wiping the coating with asolution of glycerine and water-Just prior to the transfer. The backsizing I8 may also comprise l -tives, or substituted rubber derivatives,as Duprene," Thiokol and the.l like, reclaimed rubber,

resinous materials as "Vistanex (an isobutylene polymer) and the like.

In the specification and claims where I refer to a blasting resistantmaterial or blasting resistant characteristic or blasting resistance," Imean to includethereby a physical character of resiliency, deformingunder the impact of an air blast and material entrained thereby, toreassume its normal contour without experiencing substantialabrasion,drying, or hardening, as distinguished from the objectionable warping,shrinking, expanding, drying, hardening and abrasion of other stencilingor masking materials known to me, which under the action of an air blastand materials entrained thereby, exhibit the objectionablecharacteristics referred to, after blasting. The term sandblast stencilor sandblast stencil sheet, as used in the specification and claims,denotes sheet material intended for and suitable for use in Sandblastinginscriptions on stone both before and after a stencil aperture has beencut therein. y

From the foregoing description it will be seen that I have provided alaminated sheet compris'- ing a layer of a blasting-resistant materialin the nature of a. rubber-#like sheeting including filling agentsbonded with a vulcanized or unvulcanized binder which affords easycutting, a

liner having blast-resistant properties adapted to be'permanentlyretained on one side of thel rubber-like -sheeting and abacksizing capable of taking transfer impressions, the composite beingretained on the surface to be inscribed by a pressure-sensitive adhesivewhich adheres without activation.

What I claim is:

1. As a new article of manufacture, composite sheet material having theproperties of flexibility and resistance to impact of abrasiveparticles, comprising a, rubber compounded blasti-resistant backing, apermanent liner secured to a surface of said backing, a coating adaptedLto receive transfer impressions and prevent the offsetting of adhesivethereon on the exposed surface of said composite material, and anadhesive coating on the other surface of said composite material adaptedto retain asid composite sheet material on the article to be inscribed.

2. As a new article of manufacture, laminated sheet material comprisingan inherently flexible blast-resistant rubber-compounded sheet backing,a layer of a pressure-sensitive adhesive on one y surface of saidlaminated sheet, a sheet of treated cellulosic material adhesivelysecured to the said backing, and a coating of a cellulose derivativeadapted .to receive transfer impressions on the other surface of saidlaminated sheet.

3. As a new article of manufacture, laminated sheet material comprisingan inherently exible rubber-compounded blast-resistant. backing, a

coating of a non-drying normally ressure-sensitive adhesive on onesurface of said laminated material, a liner of treated paper adhesivelysev cured to the other surface of said backing, andv a coating of thegroup comprising a cellulose derivative, glue, and casein, adapted toreceive transfer impressions and prevent the offsetting of adhesivethereon, on the other surface of said laminated material.

' stencil sheet material having the properties of 4; As a new article ofmanufacture, laminated sheet material comprising an inherently flexiblerubber-compounded blast-resistant backing, a coating of a non-dryingnormally pressure-sensitive adhesive on one surface of said backing, a"liner of treated fabric adhesively secured to the other surface of saidbacking, and a coating of the group comprising a cellulose derivative,glue, and casein, adapted to receive transfer impressions on the exposedsurface of said liner.

5. As a new article of manufacture, laminated sheet material comprisinga backing of comminuted base material bonded together by a rubberbinder, a coating of a pressure-sensitive adhesive on one surface ofsaid backing, a liner of cellulosic material adhesively secured to theother surfaceof said backing", and a coating of a cellulose derivativeadapted to receive transfer impressions on the exposed surface of saidliner.

6. As a new article of manufacture, laminated sheet material comprisinga backing of comminuted'base material bonded together by a rubber binder'and an oil modifying agent adapted to reduce the toughness of saidrubber, a coating o f a pressure-sensitive adhesive on one surface ofsaid backing, a liner adhesively secured to the other surface of saidbacking, and a coating of glue adapted to receive transfer impressionson the exposed surface of said liner.

7. As a newarticle of manufacture, laminated sheet material having theproperties of exibility and resistance to impact of abrasive particles,comprising a rubber-compounded blast-resistant backing, apressure-sensitive rubber base adhesiveon one surface of said backing,an adhesive coating on the other surface of said backing adapted tosecure thereto a liner of treated cellulosic material adapted to beretained thereon during the Sandblasting operation.

8. As a new article of manufacture, sandblast flexibility and resistanceto impact of abrasive particles, comprising a thin liner of treatedcellun losic material, coated on both surfaces with a rubber basepressure-sensitive adhesive, and a blast-resistant rubber-compoundedsheet backing, said liner being secured thereto by one of said adhesivecoatings, the other adhesive coating being adapted to retain saidsandblast stencil sheet material on a surface to be sandblasted.

1l. As a new article of manufacture, sandblast stencil sheet materialhaving the properties of flexibility and resistance to impact ofabrasive particles, comprising a thin paper liner of cellulosic materialimpregnated with a primer and coated on both surfaces with a' rubberresin presn sure-sensitive adhesive, and a blast-resistantrubber-compounded sheet backing, said liner being secured thereto by oneof said adhesive coatings, the other adhesive coating being adapted toretain said sandblast stencil sheet material on a surface to besandblasted.

12.- As a new article of manufacture, laminated sheet'material havingthe properties of flexibility stencil sheet material havingtheproperties of fiexibility and resistance to impact of abrasive othersurface of said backing securing thereto a44 unied liner of cellulosicmaterial adapted to be retained thereon during the Sandblastingoperation.

9. As a new article of manufacture, sandblast stencil sheet material inlaminated form and having the'properties of flexibility and resistanceto the impact ofabrasive particles, comprising a and resistance toimpact of abrasive particles, comprising a thin liner of cellulosicmateria1 impregnated with a rubber base solution, an adhesive coating oneach surface of said liner, a baCking layer of comminuted base'fmaterialbonded to gether by a rubber binder, said liner being retained theretoby one of said adhesive coatings, and a coating of the group ,comprisinga cellulosic derivative, glue and casein, adapted to receive transferimpressions on the exposed surface of said backing.

13. As a newl article of manufacture, laminated sheet material havingthe properties of flexibilityand resistance to impact of abrasiveparticles, comprising a thin liner of cellulosic material impregnatedwith a rubber base solution, an adhesive coating on each surface of saidliner, a backing layer of comminuted base material bonded together by arubber binder, said liner being retained thereto by one of said adhesivecoatings, and a coating of glue adapted to receive transfer impressionson the exposed surface of said backing.

14. As a new article of manufacture, laminated sheet materia1 having theproperties of flexibility` and resistance to impact of abrasiveparticles, comprising a thin liner of cellulosic materia1 impregnatedwith a priming solution, an adhesive coating on each surface of saidliner, a backing layer of comminuted base material bonded to-v gether bya rubber binder, said liner being retained thereto by one of saidadhesive coatings, and a coating of a cellulose derivative adapted toreceive transfer impressions on the exposed surface of said backing.

15. As a new article of manufacture, laminated f adapted to receivetransfer impressions on the exposed surface of said backing.A v

16. As a new article of manufacture, a stencil designed for use incutting letters, symbols or designs on a surface by way ofan abrasiveblast,

and comprising a compositesheet adapted to be placed against the surfaceand upon proper shaping thereof to control the blast 4so that it formsor cuts the desired letters, symbols or designs on saidsurface andincluding anabrasive-resistant outer layer formed of an appreciableamount of vulcanized rubber and an admixture of a material' serving torender said vulcanized rubber tough and substantially inelastic, and aninner layer comprising a permanent liner impregnated with acompositioncomprising an appreciable amount of uncured rubber, and an adhesivecoating on the exposed face of the inner layer for holding the sheet inadhesively connected relation with said surface. y A

, 17. As a new article ofY manufacture, astencil I designed for use incutting letters, symbols or designs on a surface by way of an abrasiveblast,

and comprising a composite sheet adapted to be placed against thesurface and upon proper shap-f ing thereof to control the blast so thatit forms or cuts the desired letters, symbols or designs on said surfaceand consisting of an abrasive-resistant outer layer including asubstantial amount of vulcanized rubber and an admixture of a materialserving to toughen the rubber and make it substantially inelastic, andan inner layer including a substantial amount of unvulcanized rubber init and a fibrous sheeted medium for making said unvulcanized rubbersubstantially inelastic, and an adhesive coating on the exposed face ofthe inner layer for holding the sheet in adhesively connected relationwith said surface.

18. As a new article'of manufacture, a stencil designed for use incutting letters, symbols or designs on a surface by way of an abrasiveblast, and comprising a composite sheet adapted to be placed against thesurface and uponproper shapandereV t 16 ing thereof to control the blastso that it forms or cuts the desired letters, symbols or designs on saidsurface'and including an abrasive-resistant outer layer formed of anappreciable amount of l vulcanized rubber and an admixture ofa materialserving, to render said vulcanized rubber tough andsubstantiallyinelastic, and an inner layer containing uncured rubber, and an adhesivecoating on the exposed face of the inner layer for holding the sheet inadhesively connected relation with said surface. A i

2l. As a new article ofrnanufacture, a stencil designed for'use incutting letters, symbols or designs on a surface by Way of an abrasiveblast,

and comprising a composite sheet adapted to be placed against the'surface and upon proper shaping thereof to control the blast so that itforms or cuts the desired letters, symbols or designs on said surfaceand comprising an abrasive-resistant outer layer including a substantialamount of vulcanized rubber and an -admixture of a mar terial serving totoughen the rubber and make it substantially inelastic, land an innerlayer including unvulcanized rubber in it and a material' for makingsaid innerl layer tough and substantially inelastic,- and an adhesivecoating on the exposed face of the inner layer for holding the sheet inadhesively connectedrelation with said Surface.

22. As a new article of manufacture, a, stencil designed foruseincutting letters,lsymbols or designs on a surface by way of anabrasive blast, and comprising a composite sheet adapted to be placedagainst the surface and upon proper shapmg thereof to control the blastso that it forms or cuts the desired letters, symbols or designs on saidsurface and comprising an abrasive-resistant, substantially inelasticouter layer including an impregnated fibrous sheet and an inner layerincluding a substantial amount of unvulcanized rubber and an admixtureof a toughening agent comprising glue, and an adhesive coating on theexposed face of the inner layer for holding the sheet in adhesivelyconnected relation with said surface.

19. As a new article of manufacture, a sandblast stencil sheet materialhaving the propertiesof flexibilityand resistance to impregnation ofabrasive particles, comprising a fibrous sheet per.

manent liner impregnated with a primer and coated on both surfaces withan adhesive, and a blast-resistant rubber-compounded sheet backing, saidliner being secured thereto by one of said adhesive coatings, the otheradhesive coating being v adapted to retain said sandblast stencil sheetmaterial on a surface to besandblasted.

20. As a new article of manufacture; a. stencil designed. for use incutting letters, symbols or designs ona surface by way of an abrasiveblast, and comprising a composite sheetadapted to be placed against thesurface and upon proper shaping thereof to control the blast so that itforms or cuts the desired-letters, symbols or designs on said surfaceand comprising an abrasive-resistant outer layer embodying an'appreciable amount of vulcanized rubber and an admixture of aniadesigned for use in cutting letters, symbols ordesigns on a surfaceby way of an abrasive blast,

and comprising a composite sheet adapted to be placed against thesurface and upon proper shaping thereof to control the blast so that itforms. or cuts the desired letters, symbols orrdesigns on said surfaceand comprising a comparatively thin abrasive-resistant outer layerembodyingva substantial amount of vulcanized rubber and an admixture ofa material serving to render the vul- Y canized rubber tough andsubstantially inelastic,

and an inner layer of less thickness than the outer layer andincludingunvulcanized rubber l,in it and in addition embodying amaterial .whereby said inner` layer is'also rendered tough andsubstantially. inelastic, and an adhesive-coating on the kexposed faceof the inner layer for holding the sheet in adhesively connectedrelatlonwith said surface.

ALFRIEIDv `J. WARTHA.

Certificate of Correction Patent No. 2,410,472. November 5, 1946.

ALFRED J. WARTHA It is hereby certified that errors appear in theprinted specification of the above numbered patent requiring correctionas follows: Column 3, line 19, for Wil read will; lines 64 and 69, forthe Word writing read whit'ing; column 11, line 24, before condensationinsert a; column 12, line 74, claim 1, for asid read said; column 13,lines 13 and 14, claim 3, for ressure-sensitive read pressure-sensitive;and that the said Letters Patent should be read With these correctionstherein that the same may conform to the record of the case in thePatent Ofce.

Signed and sealed this 30th day of March, A. D. 1948.

THOMAS F. MURPHY,

Assistant Commissioner vof Patents.

